The invention relates to a method and an arrangement for decomposing organic waste water pollutants by using freely suspended bacteria.
In the course of increased problems with drinking water and ground water, the treatment of waste water, in particular the decomposition of organic waste water pollutants, becomes more and more important. In the communal area, the waste water costs charged to the entity causing them were calculated in accordance with peak values of pollutants. Therefore large fluctuations in waste water concentrations lead to considerable increases in waste water costs. For reasons of costs, many industrial enterprises, in particular those with strong fluctuations in waste water concentrations, locate the purifying of waste water directly at the source of waste water generation. Communal treatment facilities can be relieved by this and waste water costs can be saved.
So-called partially aerobic methods have proven themselves in the decomposition of organic waste charges in high-concentration waste water, wherein aeration of the waste water and, if required, the addition of minimum materials to the waste water while regulating the redox potential takes place. It is known that under the conditions of the partially aerobic method the enzymes of the respiratory chain of the bacteria, or respectively the microorganisms are particularly active. Only a comparatively small portion of the pollutants is used for building the biomass. The preponderant portion of the pollutants is directly converted into carbon dioxide (CO.sub.2) and water (H.sub.2 O). It is important that the supplied amount of air is metered in such a way that the bacteria can bring the redox potential of their medium into optimal and respiratory-active conditions. It was found that, with an increase in the redox potential by increasing the air supply, increased flocculation can occur.
Although a decrease of the redox potential below -300 mV decreases the danger of flocculation, it worsens the degree of the decomposition effects of the bacteria.
A partially aerobic method is known from DE-OS 32 27 488, wherein it is intended to set the redox potential to as constant as possible a value between -200 mV and -300 mV, and the pH value also essentially constant in the range between 7.0 and 9.0, preferably 8.0 to 8.1.
However, in actuality it has been shown that critical concentration fluctuations and above all changes in the pH values in the waste water could no longer be optimally regulated by means of the known partially aerobic method, and that the decomposition activity of the microorganisms is possibly reduced.